Support unit tests written in Clarity - #[test]

[lgalabru]

A non negligible amount of developers want to write their tests in clarity.
I wonder if this is something we could support "simply" by introducing a #[test] command processor.
It could look like:

(define-public (increment-counter (step uint))
    (+ step (data-var-get counter)))

;; #[test]
(define-public (test-increment)
    (asserts! (is-eq u1 (increment-counter u1)) (err u1001)))

I think we would still be using js/ts for coordinating / structuring the test execution, but at least the logic would be written in clarity - developers would be calling something like:

describe("Counter contract tests", () => {
  it("ensures counter is counting", () => {
    const { result, events } = simnet.assertPublicFn(
      "counter",
      "test-increment",
      [Cl.uint(1)],
      deployer,
    );
  });
});

So when deploying such contracts, I think the #[test] directive would exclude the subsequent clarity statement from the contract?

[hugocaillard]

@lgalabru What do you think about the clarunit approach? https://www.npmjs.com/package/@stacks/clarunit
(Similar ideas)

[lgalabru]

Oh nice, that probably works. I guess with this present proposal, clarity testing clarity would become a first class citizen.
We can keep this issue open for a few week and passively collect feedbacks / demands?

[BowTiedRadone]

@lgalabru Users can now write property-based tests and define invariants to fuzz test their Clarity smart contracts directly in Clarity, using Rendezvous.

Rendezvous allows randomly generated arguments to be passed to test functions, making it possible to exercise smart contracts more rigorously without relying entirely on the classic hand-written test scenarios.